The Pacific Decadal Oscillation (PDO) is a linked ocean-atmosphere alternation of warm and cool sea surface temperatures in the northern and eastern Pacific, on the scale of several years to over a decade. There are several drivers, which include the El Nino (ENSO) oscillation, random atmospheric variation and, according to recent research, anthropogenic global warming. As with the Arctic Multidecadal Oscillation, this is an area of active research with no well-defined consensus, but the trend is toward considering it a natural variation, and not a rhythmic oscillation.
***
That is not to say it is entirely a mirage: positive and negative events are correlated with other phenomena. But with such irregular period and magnitude, the PDO can’t well be called a cycle. As Michael Mann theorizes, the PDO is more likely manifesting the planet’s warming trend.
The positive phase of the PDO involves cool sea surface temperatures (SSTs) in the north midlatitudes from south of Alaska west to Japan, while the equatorial region of the eastern Pacific is warm. The negative phase is the opposite: warm in the northern midlatitudes, cool in the equatorial region.
Linkages between the PDO and ENSO can have considerable lag times, of up to three years, as the connections involve slow oceanic Rossby waves and mixing processes down to mid-depths of several hundred meters. The magnitudes of PDO events can vary on the scale of years to several decades.
The Pacific Decadal Oscillation is associated with variations in weather across the Pacific. A positive cycle is correlated with warmer than average weather throughout western North America, Alaska, western Canada and Australia, and cooler weather in the Gulf region, eastern Canada and eastern Siberia, and a less active than usual Indian monsoon. Precipitation is above average along the west coast of North America, and below average in Siberia, Canada, the Gulf region and Australia
The negative phase comes with the opposite: cooler weather than normal across the west coast of North America, Alaska, western Canada and Australia, warmer weather in the Gulf region, eastern Canada, and Siberia, and a more active Indian monsoon. Precipitation is below average along the west coast of North America, and above average in Siberia, Canada, the Gulf region and Australia.
Tomorrow: the North Pacific Gyre Oscillation.
Be brave, and be well.
—
This post was previously published on Dailykos.com and is republished on Medium.
***
You Might Also Like These From The Good Men Project
 |
 |
 |
 |
Join The Good Men Project as a Premium Member today.
All Premium Members get to view The Good Men Project with NO ADS.
A $50 annual membership gives you an all access pass. You can be a part of every call, group, class and community.
A $25 annual membership gives you access to one class, one Social Interest group and our online communities.
A $12 annual membership gives you access to our Friday calls with the publisher, our online community.
Register New Account
Need more info? A complete list of benefits is here.
—
Photo credit: iStock
